System for controlling the flow of molten metal



Oct. 30, 1956 E. FQw. ALEXANDERSON ,7 3

SYSTEM FOR CONTROLLING THE FLOW '01-" MOLTEN ME A;

Filed April 20, 1953 2 Sheets-Sheet 1 Fig.l.

INVENTOR ATTOR N EY E i'nst F.W. Alexunderson.

Oct. 30, 1956 E. F. w. ALEXANDERSON 2,768,413

SYSTEM FOR CONTROLLING THE'FLOW 0F MOLTEN METAL Filed April 20, 1953 2Sheets-Sheet 2 INVENTOR ErnstEwAlexonderson.

United States Patent 2,768,413 SYSTEM FOR CONTROLLING THE FLOW OF MOLTENMETAL Ernst F. W. Alexanderson, Schenectady, N. Y., assignor toAllegheny Ludlum Steel Corporation, Brackenridge,

Pa., a corporation of Pennsylvania Application April 20, 1953, SerialNo. 349,846 3 Claims. (Cl. 2257.2)

This invention relates to the pouring of molten metal, and in particularto a system and apparatus for controlling the flow of molten metal inthe making of castings.

In casting molten metal, it is desirable to control the flow of suchmolten metal into a mold so as to obtain a sound homogeneous casting.This is especially true in the casting of stainless steel, and inparticular in the making of continuous castings of steel or othermetals. In the continuous casting of steel it is desired to maintain asubstantially constant level of molten metal above the solidifiedcasting to insure a substantially constant solidification rate and asound casting.

Heretofore many attempts have been made to control the pouring of suchcastings, but the known controls have been based primarily on a manuallyinitiated control operation resulting from the actions of an operatordependent upon a visual observation of the pouring action. Such priorart operations have not proven to be satisfactory and have frequentlyresulted in castings so faulty that they had to be scrapped.

An object of this invention is the provision of an automatic control forcontrolling the pouring of molten metal from a tundish to a mold.

Another object of this invention is to provide an electrical systemresponsive to the level of molten metal in a mold for controlling theflow of molten metal from a tundish to the mold.

A further object of this invention is to provide a system forcontrolling the flow of molten metal from a tundish supplied by atiltable furnace in response to the level of molten metal in a moldsupplied from the tundish, the system including means for controllingthe tilting of the furnace simultaneously with controlling the flow fromthe tundish.

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawings inwhich:

Figure 1 is a diagrammatic view of circuits and apparatus embodying theteachings of this invention;

Fig. 2 is a diagrammatic view of a specific control circuit which can beemployed as a modification of a part of the system illustrated in Fig.l; and

Fig. 3 is a diagrammatic view of circuits and apparatus illustratinganother embodiment of this invention.

Referring to the drawing, and in particular to Fig. 1, this invention isillustrated by reference to a system for controlling the flow of moltenmetal from a tundish shown generally at 12 into a mold 14, the moltenmetal being supplied to the tundish 12 from a tiltale holding furnace orladle illustrated schematically at 16.

The tundish 12 is formed of refractory material and as illustrated is ofa general conical design terminating in a downwardly depending portion18 having an orifice 2i centrally disposed therethrough. The tundish 12in this instance is provided with a centrally disposed core member 22 ofrefractory material, the core member 22 being provided with openings 24at the lower end thereof for permitting passage of molten metal fromabout the core portion 22 into the orifice 20. Adjacent the upper end ofthe tundish 12 is a liner 26 of refractory material of general dishshape having openings 28 in the bottom thereof communicating with thespace formed between the core 22 and the side walls of the tundish 12.The

core member 22 and/or the liner 26 may be secured in assembled relationin the tundish 12 in any suitable manner, such as by cementing them inposition. The purpose of the core member 22 is to so displace moltenmetal in the tundish 12 that in practice a ring of molten metal will heformed between the core member 22 and the side Wall of the tundish 12,the purpose of which will be explained more fully hereinafter.

The mold 14 may be any suitable type of mold, although in this instanceit is illustrated as being the upper end of a continuous casting type ofmold. Thus the mold 14 is provided with an inner mold wall 30 of copperor other good thermally conductive metal, the upper end being surroundedby a water cooling jacket 32 for ex tracting heat from the mold wall 30.Although not illustrated, the downwardly depending portion 18 of thetundish 12 which is in alignment with the mold cavity of the mold 14 andthe upper end of the mold 14 may be suitably housed to retain aprotective atmosphere therein to prevent oxidation and othercontamination of the molten metal as it flows from the tundish 12 intothe mold 14. As is well-known, with a continuous casting mold 14 thesolidified cast metal is withdrawn from the bottom of the mold 14 at asubstantially constant rate and it is desired to maintain the level ofthe molten metal in the mold 14 at the predetermined level 34illustrated in order to obtain a substantially constant rate ofsolidification of the metal as the cast metal is withdrawn from the mold14.

The tiltable furnace or ladle 16 may be of any suitable type forcontaining a supply of the molten metal 12 and delivering such moltenmetal to the tundish 12 at a controlled rate for cooperating with thetundish, as will be explained more fully hereinafter, to control therate of flow of molten metal from the tundish 12 to the mold 14. In thisinstance the tiltable furnace 16 is schematically illustrated as havinga rack and pinion gear drive 36 disposed for operation to control thetilting of the furnace 16 and thereby control the flow of molten metalsupplied to the tundish 12.

In order to apply a force to the molten metal in the tundish 12 tocontrol the flow therefrom, current is induced in the ring of moltenmetal formed by the core member 22 within the tundish 12. For thispurpose a water-cooled induction coil 38 is so disposed about thetundish 12 as to extend along the outer wall thereof a distancesubstantially equal to the length of the core member 22 and consequentlysubstantially equal to the height of the ring'of molten metal in thetundish 12. Energy is supplied to the induction coil 38 from atransformer 40, the primary windings of which are connected to a sourceof alternating current. Thus as current flows in the induction coil 38,which is illustrated as of the water-cooled type, an electromagneticrepulsion is developed between the current flowing in the coil 38 andthe current induced thereby in the ring of molten metal within thetundish 12 to effectively retard the flow of molten metal from thetundish 12 to the mold 14. The degree of such electromagnetic repulsionwill'of course depend upon the magnitude of the current flow in theinduction coil 38.

The current flow in the induction coil 38 is controlled by controllingthe saturation of a pair of reactors 42 and 44 connected in circuitrelation With the transformer 4t), the degree of saturation thereofbeing controlled by the operation of a dynamo-electric machine 46 inresponse to a measure of the change in the level of the molten metalfrom the predetermined level 34 which is to be maintained in the mold14. The reactors 42 and 44 are formed of rectangular laminated coremembers 48 and 50-, respectively, having a main winding-52am 54, respectively, and a direct current control winding 56 and 58, respectively,disposed thereon.

In order to control the current flow in the series connected directcurrent windings 56 and 58 of the saturable reactors 42 and 44, thedynamo-electric machine 46 is connected so that its output current flowsthrough such windings. In this instance the dynamo-electric machine 46is of the Well-known amplidyne type and is driven by any suitabledriving means such as an induction motor (not shown). Thedynamo-electric machine 46 is provided with two sets of brushes per pairof poles and is illustrated as being a 2-pole machine. One set of thebrushes 60 is connected to the load illustrated as being the seriesconnected direct current windings 56 and 58 of the saturable reactors 42and 44 and the other set of brushes 62 is short circuited. The twomutually perpendicular brush axes are commonly known as the control axisand the short circuit axis, respectively. In this instance thedynamo-electric machine 46 is illustrated as having three field windings64, 66 and 68, the field winding 64 being a shunt field Winding whichfunctions as a delayed negative feedback to render the operation of thedynamo-electric machine responsive to a rate of change to preventhunting in the operation thereof. The winding 66 is connected through anadjustable resistor 70 to a constant direct current source representedby conductors 65 and 67 to function as a bias winding, the degree ofenergization of which is controlled by adjusting the resistor 70. On theother hand, the field winding 68 constitutes a control field winding forthe dynamo-electric machine 46 and while the winding 68 is illustratedas being connected across the direct current source of supply, thedegree of energization of the winding 68 is dependent upon a measure ofthe level of molten metal in the mold 14. The windings 66 and 68 aredisposed in opposition to each other to control the output of themachine 46.

In order to control the energization of the control field winding 68, asensing means 72 is utilized for giving a signal which is a measure ofthe level of the molten metal in the mold 14. In this instance thesensing device 72 is illustrated as being a thermostat sensing device ofthe type knownto the trade as a thermosaul which is embedded in the moldwall 30 of the mold 14 at substantially the height of the level ofmolten metal which is to be maintained in the mold 14. As the mass ofmolten metal in the mold 14 rises, the thermosaul will give an increasedsignal in response to the increase in tempera ture occasioned byincreasing such mass, or the signal will be diminished as the level ofmolten metal lowers from the level which is to be maintained in directproportion to the decrease in the mass. Since the signal from thesensing device 72 is normally too small for control purposes, suchsignal is supplied to an amplifier illustrated generally at 74, theoutput of the amplifier 74 being connected in circuit relation with thecontrol field winding 68 of the dynamo-electric machine 46. Since manydifferent types of amplifiers are well-known and can be em ployed inthis system, the details of the amplifier are not illustrated, theamplifier being represented by the rectangle 74. The output of theamplifier 74 is connected in opposition to the polarity of the normalsupply of energy for the control winding 68 so that as the output of theamplifier 74 increases in response to a measure of the rise of the levelof the molten metal in the mold 14, the net energizing elfect of thecontrol field winding 68 is decreased insofar as the operation of thedynamoelectric machine 46 is concerned. This is apparent when it isconsidered that the control field winding 68 is normally connected as byconductor 76 to the positive conductor 65 of the source of directcurrent energy and by conductor 78 through the amplifier 74, a portionof an adjustable rheostat 80 and conductor 82 to the negative conductor67 of the source of direct current supply whereas the amplifier 74 isconnected through a circuit 4 which extends from the amplifier 74through conductor 78, the field winding 63, conductor 76 and anotherportion of the adjustable rheostat 80 and conductor 79 back to theamplifier 74.

The tiltable furnace or ladle 16 is disposed to be driven in a directionto tilt the furnace to supply the molten metal to the tundish 12 as themolten metal flows from the tundish to the mold 14. For this purpose,the rack and pinion drive 36 of the furnace 16 is connected to be drivenby a motor 84 disposed to be connected as by conductors 86 and 88 to asource of direct current supply represented by conductors 85 and 87. Inorder to auto matically control the energization of the motor 84, acontact member 90 of a toggle switch 91 is disposed to be intermittentlyactuated into circuit closing position to establish the energizingcircuit for the motor 84. Another contact member 92 is disposed to bemanually operated to also establish such energizing circuit for themotor 84 where it is desired to increase the tilting of the furnace 16at a faster rate than the intermittent operation of the contact member90 permits. As illustrated, the contact member 90 of the switch 91 iscarried at one end of a pivotally mounted arm 94 which is normallybiased as by means of a spring 96 to actuate the contact member 90towards the circuit closing position. However, the operation of thecontact member 90 is controlled as by means of a cam 98, the cam surfaceof which is disposed to engage the free end of the pivotal arm 94 toeifect the intermittent operation of the contact member 90 as the cam 98is driven.

In order to control the operation of the cam 98 and consequently controlthe intermittent operation of the contact member 90, the cam 98 isconnected to be driven by a motor 100 which is connected to be suppliedfrom the constant direct current source of supply represented byconductors 65 and 67. However, in order to control the operation of themotor 100, the motor 100 is also connected across the output of thedynamo-electric machine 46, such output being in opposition or buckingrelation to the normal energization of the motor 100. Thus the motor isconnected as by conductor 102 to the conductor 67 of negative polarityof the direct current source of supply and is connected as by conductors104 and 106 through the dynamo-electric machine 46, conductor 108, aportion of an adjustable rheostat 110 and conductor 112 to the conductor65 of positive polarity of the direct current source. At the same timethe dynamo-electric machine 46 is connected by a circuit extending fromone of its terminals through conductors 106 and 104, the armature of themotor 100, conductor 102, the negative conductor 67 of the source ofsupply, conductor 114, another portion of the adjustable rheostat 110and conductor 108 to the other terminal of the dynamo-electric machine46 to oppose the normal energization of the motor 100.

In operation, assuming that the level of the molten metal in the mold 14is at the predetermined level 34 which is to be maintained, then themotor 84 functions to drive the tiltable furnace 16 at a rate sufficientto merely supply metal to the tundish 12 at a rate to offset the flow ofmolten metal from the tundish to the mold 14. At the same time thedynamo-electric machine 46 is energized to control the saturation of thesaturable reactors 42 and 44 so that the current flow in the inductioncoil 38 is at a value that the retardation action on the ring of moltenmetal in the tundish 12 is sufiicient to cooperate with the supply ofmolten metal from the furnace 16 to the tundish 12 to normally controlthe flow of molten metal from the tundish 12 to the mold 14 to maintainthe level of molten metal therein at the predetermined level 34.

If, for any reason, the level of the molten metal rises above thepredetermined level 34 which is to be maintained in the mold 14, thetemperature of. the sensing device 72 increases with the result that thesignal which is a measure of such a rise in the level, is increased,whereby the output of the amplifier 74 is increased. Since the output ofthe amplifier 74 is in opposition to the normal energization of thecontrol field winding 68, the increase in the output of the amplifier 74functions to effect a net decrease in the energization of the controlfield winding 68 with the result that the effect of the biasing winding66, which is normally in opposition to the effect of the field winding68, increases to eifect an increase in the output of the dynamo-electricmachine 46. As the output of the dynamo-electric machine increases, moredirect current flows through the control windings 56 and 58 of thesaturable reactors 42 and 44, respectively, to increase the saturationthereof whereby an increase in the current flow in the induction coil 33is effected to increase the electromagnetic repulsion developed in thering of molten metal Within the tundish 12 to effectively retard theflow of molten metal from the tundish 12 to the mold 14. At the sametime that the output of the dynamo-electric machine 46 is so increased,the field winding 64 senses such a change to effect a rate of change inthe energization of the dynamo-electric machine 46 in direct proportionto the rate of such an increase in the output thereof to adjust the netexcitation of the dynamo-electric machine .46 in accordance with therate of change effected in the change of the flow of the molten metal tothereby prevent overshooting in the control of the energization of theinduction coil 38.

Simultaneously with the change in the flow of current in the inductioncoil 38, the dynamo-electric machine 46 functions to buck the normalenergization of the motor 100 to effect a decrease in the speed ofoperation of the cam 98 and thereby effect a decrease in theintermittent operation of the contact member 90 of toggle switch 91 todecrease the speed of the operation of the motor 84. Such a decrease inthe speed of operation of the motor 34 effectively decreases the tiltingspeed of the furnace 16 to decrease the flow of molten metal therefromto the tundish 12. The decrease in the flow ofmoltenmetal caused by aslowing of the tilting operation of the furnace 16 cooperates with theelectromagnetic repulsion retardation developed in the ring of metal inthe tundish 12 to effectively decrease the flow of molten metal from thetundish 12 to the mold 14 to cause the level of the molten metal in themold 114 to return to the predetermined level 34 which is to bemaintained.

If, on the other hand, the level of molten metal in the mold 14 fallsbelow the level 34 which is to be maintained, then the sensing device 72provides a decrease in the signal therefrom in response to the decreasein the mass of the metal in the mold 14 with the result that the outputof the amplifier 74 is decreased. Such a decrease in the output of theamplifier 74 causes an increase in the energization of the control fieldwinding 68 in opposition to the effect of the bias field winding 66 withthe result that the output of the dynamo-electric machine 46 decreasesto effect a decrease in the current flow in the control windings 46 and58 of the saturable reactors 42 and 44, respectively. Such a decrease inthe current flow in the control windings 56 and 58 of the reactors 42and 44, respectively, decreases the saturation thereof with the resultthat less current flows in the induction coil 38 and less of a retardingaction is applied to the ring of molten metal within the tundish 12 withthe result that the fiow of molten metal from the tundish 12 to the mold14 is increased to tend to raise the level of molten metal therein tothe predetermined level 34 which is to be maintained. At the same timethe shunt field winding 64 senses the rate of change in the output ofthe dynamo-electric machine 46 to prevent an operation thereof to effectan overshooting in the corrective action applied to the induction coil38.

Simultaneously with the change in the energization of the induction coil38, the decreased output of the dynamo-electric machine 46 in oppositionto the constant source of supply to the cam motor causes an increase inthe speed of operation of the cam motor 100 with the result that thereis an increase in the intermittent operation of the contact member 90 toeffect an increase in the speed of operation of the furnace motor 84.Such an increase in the speed of operation of the motor 84 increases thespeed of operation of the rack and pinion drive 36 with the result thatthe furnace 16 is tilted at a faster rate to increase the supply ofmolten metal to the tundish 12 simultaneously with the decrease in theretarding force applied by the induction coil 38. The control of thetilting furnace 16 thus cooperates with the change in the energizationof the induction coil 38 to effectively increase the rate of flow of themolten metal from the tundish 12 to the mold 14 to return the level ofthe molten metal therein to the predetermined level 34 which is to bemaintained.

If, during the operation just described, it is desired to effect anincrease in the supply of the molten metal to the tundish 12 at a fasterrate than that obtained through the automatic control of the operationof the furnace tilting motor 84, then the contact member 92 can bemanually operated to a circuit establishing position to continuouslyenergize the furnace motor 84 to effectively tilt the furnace 16 at afaster rate than the tilting rate obtained through the operation of thecam motor 1% and toggle switch 91.

If, in addition to controlling the rate at which the furnace 16 tilts,it is desired to provide for returning the furnace 16 to a vertical ornon-pouring position or to definitely stop the pouring of the moltenmetal from the furnace 16 at any point during the operations previouslydescribed, a circuit as illustrated in Fig. 2 can be employed forcontrolling the tilting of the furnace 16. In this embodiment thefurnace motor 84 comprises a field winding 116 disposed to be energizedfrom a suitable direct current source represented by conductors 118 and126 and an armature winding 122 connected by conductors 124 and 126 tobe supplied with energy from a generator 12$ that is driven by analternating current motor 130 and excited by an excitor generator 132.The main generator 128 comprises an armature winding 134, one terminalof which is connected to the conductor 124 and the other terminal ofwhich is connected through a self energizing field winding 136 to theconductor 126 for supplying the motor 84, and a field winding 138disposed to be supplied with energy from the armature winding 1451 ofthe eXcitor generator 132. The

excitor generator 132 illustrated is provided with a field winding 142,connected across the main generator 128 to be energized in accordancewith the output thereof and two control field windings 144 and 146 whichare disposed to be energized in opposition to each other and willfunction to control the excitation of the excitor generator 141?. Thecontrol field winding 144 is disposed to be connected through a manuallyoperated contact member 148 to the source of direct current energyrepresented by the conductors 118 and whereas the field winding 146 isdisposed to be connected by the intermittently operated contact member90 of toggle switch 91 across the direct current source of supply or bya manually operated contact member 92 across the direct current sourceof supply.

If the cam 98 is driven in the manner described with reference to thecontrol circuit of the embodiment of Fig. 1, then the contact member 90is intermittently operated to a circuit closing position to effect theintermittent energization of the control field Winding 146 to so controlthe excitation of the excitor generator 122 as to control the excitationof the main generator to effectively energize the motor 84 to drive therack and pinion drive 36 in a direction to tilt the furnace 16 at a ratedepending upon the rate of intermittent operation of the contact member90 of toggle switch 91. Again, as in the previous embodiment, if it isdesired to tilt the furnace 16 at a faster rate than is obtained throughthe intermittent operation of the contact member 90, the contact member92 can be manually operated to establish the energizing circuit for thecontrol field winding 146 to effectively increase the energizationthereof in a direction to cause the operation of the motor 84 in adirection to tilt the furnace 16 at a faster rate.

If, at any time during the operation, it is desired to stop the flow ofmolten metal from the furnace 16 to the tundish 12, or upon completionof the pouring operation, it is desired to return the furnace 16 to avertical position, then the contact member 148 can be manually operatedto a circuit closing position to effect the energization of the controlfield winding 144. If such energization of the control field Winding 144is effected during the intermittent operation of the contact member 90,the continuous energization of the field winding 144 during the manualoperation of contact member 148 will predominate over the intermittentenergization of the control field winding 146 occasioned by theoperation of contact member 90 to so control the excitation of theexcitor generator 132 as to effect an operation thereof in a directionto control the excitation of the main generator 128 to cause a reversalof the direction of operation of the motor 84. Such reversal of themotor 84 stops the tilting operation of the furnace 16 and ifmaintained, will operate the rack and pinion drive 36 in a direction toeffect a reversal in the tilting operation of the furnace 16 to returnthe furnace 16 to a vertical position. Thus a fast decrease in the flowof molten metal from the furnace 16 to the tundish 12 can be obtainedduring any normal operation of the cam 98 in response to an operation ofthe dynamoelectric machine 46. As will be appreciated, upon thecompletion of a pouring operation from the furnace 16, the furnace 16can be returned to its vertical position by maintaining the contactmember 148 in its circuit closing position to maintain the energizationof the control field winding 144 to effectively drive the motor 84 in adirection to return the furnace 16 to a vertical position.

Instead of the electromagnetic control as described with reference toFig. l of the drawing, an electromechanical control can be utilized forcontrolling the flow of molten metal from the tundish 12 to the mold 14.Such a system is illustrated in Fig. 3 of the drawing, like numerals ofFigs. l and 2 being employed for designating like pieces of apparatusand parts of the circuits. In the embodiment of Fig. 3 the tundish 12can be of any suitable construction and is provided with a plungermember 150 disposed to be actuated into the molten metal in the tundish12 to displace metal therein to thereby raise the static head of moltenmetal above the orifice to control the flow of the molten metaltherefrom to the mold 14. The plunger 150 in this instance is formed ofrefractory material and is of general conical shape to conform to theinner shape of the side walls of the tundish 12. As illustrated, theplunger 150 is carried by an arm 152 which is secured to a mechanicallinkage 154, one end of which is pivotally secured to a fixed bracket156, the other end of the linkage 154 being secured to the pinion of therack and pinion drive 157 whereby an operation of the drive 157 willeffect a vertical movement of the plunger 150 into or out of the tundish12.

In the embodiment of Fig. 3, the same type of sensing device 72 isemployed for providing a signal that is a measure of the level 34 ofmolten metal in the mold 14, the signal being amplified as by means ofthe amplifier 74. In this case, however, the output of the amplifier issupplied to the control winding 158 of a magnetic amplifier 160, theoutput of which is disposed to control the energization of the controlfield winding 68 of the dynamo-electric machine 46. The magneticamplifier 160 is of usual construction being formed of two rectangularlaminated core members 162 and 164 each of which is provided with a mainwinding 166 and 168, respectively, the control winding 158 being commonto both of the laminated core members 162 and 164. The main windings 166and 168 are connected in parallel circuit relation with each other andare disposed to be connected as by conductors 170 and 172 across analternating current source of supply and by conductors 174 and 176 tothe control field winding 68. Rectifiers 178, 180, 182 and 184 areconnected in circuit relation with the main windings 166 and 168 andbetween such windings and the control field winding 68 as illustratedfor supplying a unidirectional current to the control field winding 68.

The dynamo-electric machine 46 is similar to that illustrated in theembodiment of Fig. 1, except that in this instance another field winding188 is added which functions to provide a position signal indicator forreflecting a change in the energization of the dynamo-electric machine46 in response to an adjustment of the position of the plunger 150within the tundish 12. In order that such a measure of the change of theposition of the plunger 150 will be reflected by the control winding188, the control winding 188 is connected in circuit relation with apotentiometer 190, the contact arm 192 of which is disposed to bepositioned in accordance with the operation of the rack and pinion drive157. Thus the position signal control winding 188 is connected in acircuit which extends from the conductor of the direct current source ofsupply through the armature windings of a motor 194 which is connectedto drive the cam 98, field winding 188, a resistor 196, contact arm 192of the potentiometer 190, a portion of the potentiometer 190 andconductor 198 to the conductor 87 of the direct current source ofsupply. Since the motor 194 is connected in series circuit relation withthe field Winding 188, the energization of which is controlled by theoperation of the potentiometer 190, it is apparent that the operation ofthe motor 194 and consequently the cam actuated contact member of toggleswitch 91 is directly controlled by the drive 157 which positions theplunger and adjusts the position of the contact member 192 of thepotentiometer 190.

In the embodiment of Fig. 3, the dynamo-electric machine 46 is connecteddirectly across the armature of a motor 280 which is connected to drivethe rack and pinion drive 157, it being understood that such operationwill be affected by the energization of the rate of change excitation ofthe field winding 64 and the position signal of the field winding 188 ofthe dynamo-electric machine 46 to prevent an overshooting in the controloperation of the system.

In operation, assuming that the system is operating with the level ofthe molten metal in the mold 14 at the predetermined level 34 which isto be maintained so that the signal from the sensing device 72 isadequate to provide a predetermined saturation of the magnetic amplifierto give a predetermined energization of the control field winding 68 tobalance the effect of the opposing bias winding 66, then thedynamo-electric machine 46 has been operated to effect a positioning ofthe plunger 150 to maintain a static head of the molten metal in thetundish 12 and the potentiometer has been automatically adjusted toregulate the speed of the motor 194 and consequently the tiltingoperation of the furnace 16 so that the flow of molten metal from thefurnace 16 is just suflicient to replace the metal flowing from thetundish 12. The furnace 16 and the plunger 150 thus cooperate to socontrol the flow of molten metal from the tundish 12 as to maintain thelevel of the molten metal in the mold 14 at the predetermined level 34which is to be maintained.

If, for any reason, the level of metal in the mold 14 should rise abovethe predetermined level 34 which is to be maintained, an increasedsignal is supplied by the sensing device 72 to the amplifier 74 and theamplified output thereof is impressed on the control winding 158 of themagnetic amplifier 160. This increase in the current flow in the controlwinding 158 of the magnetic amplifier 160 so increases the saturation ofthe magnetic amplifier as to effect an increase in the energization ofthe field winding 68 whereby the field winding 68 cooperates with theopposing bias winding 66 as to give a net effective excitation of thedynamo-electric machine 46 to cause it to operate so that the outputthereof effects an operation of the motor 269 in a direction to drivethe rack and gear drive 157 in a direction to actuate the linkage 154 toraise the plunger 150 thereby lowering the static head of molten metalcontained in the tundish 12. At the same time the operation of the rackand pinion drive 157 effects an operation of the contact arm 192 of thepotentiometer 190 to drive the arm in a counterclockwise direction toconnect more of the potentiometer 190 in circuit relation with theposition signal field winding 188 and the cam motor 194. Such anadjustment of the potentiometer 199 provides a change in theenergization of the dynamo-electric machine 46 refiecting the adjustmentin the position of the plunger 150 and at the same time decreases thespeed of operation of the motor 194 to slow the operation of the cam 98and consequently to effect a decrease in the number of the intermittentoperations of the contact member 96 of the toggle switch 91 to decreasethe excitation of the motor 84. As the motor 84 is thus operated aslower speed, or less frequent number of operations, the rack and piniondrive 36 of the furnace 16 is operated at a slower rate so that thetilting of the furnace 16 is effected at a slower rate to decrease theflow of molten metal from the fur nace 16 to the tundish 12. Thus as thestatic head of metal in the tundish 12 is lowered by raising the plunger150 and as the flow of metal supplied to the tundish 12 is decreased,they cooperate to effect a decrease in the flow of metal to the mold 14whereby the level of the molten metal returns to the predetermined level34 which is to be maintained.

On the other hand, if the change in the level of the molten metal in themold 14 is such as to effect a lowering of the level from thepredetermined level 34 which is to be maintained, the signal from thesensing device 72 and consequently the output of the amplifier 74 isdecreased in a direct measure with respect to the change in the level ofthe molten metal in the mold 14. As the output from the amplifier '74 isdecreased, the output from the magnetic amplifier 160 is correspondinglydecreased to effect a decrease in the energization of the control fieldwinding 68. With such a decrease in the energization of control fieldwinding 68, the bias field winding 66 will predominate to effect anexcitation of the dynamo-electric machine 46 in a direction to cause theoutput therefrom to reverse and effect a reverse operation of the motor200. Such an operation of the motor 200 effects an operation of the rackand pinion drive 157 of the linkage 154 to cause a movement thereof toeffectively lower the plunger 150 into the tundish 12 to raise thestatic head of molten metal in the tundish 12 above its orifice 20. Atthe same time the rack and pinion drive 157 of the linkage 154 actuatesthe contact arm 192 of the potentiometer 190 in a clockwise direction tode crease the amount of resistance in circuit relation with the positionfield winding 188 and the motor 194. It is thus seen that a change inthe position of the plunger 150 is directly reflected in the excitationof the dynamoelectric machine 46 and that such change also effects anincrease in the speed of operation of the motor 194 to drive the cam 198to increase the frequency of the intermittent operation of the contactmember 90 of the toggle switch 91 to effectively increase the rate ofoperation of the furnace motor 84. Such an operation of the motor 84effects an operation of the rack and pinion drive 36 of the furnace 16to increase the tilting rate of the furnace 16 and thereby increase theflow of molten metal from the furnace 16 to the tundish 12. Bysimultaneously lowering the plunger 150 to raise the static head ofmolten metal the 12 and increasing the flow of molten metal from thefurnace 16 to the tundish 12, there is obtained an increase in the rateof flow of the molten metal from the tundish 12 to the mold 14 to returnthe level of molten metal therein to the predetermined level 34 which isto be maintained.

The systems for controlling the flow of molten metal describedhereinbefore as representative of this invention are of relativelysimple design being formed of standard components. Such systems can bereadily reproduced by anyone skilled in the art. They are very efficientin operation giving a very close control vof the rate of flow of metalfor maintaining a predetermined level of molten metal in a mold.

I claim:

1. In a system for controlling the flow of molten metal from a tundishsupplied by a tiltable furnace to a mold disposed to receive the metal,the combination therewith of, a plunger disposed to be actuated todisplace molten metal in the tundish, drive means disposed fordirectional operationv to directionally actuate the plunger, adynamoelectric machine connected to control the directional operation ofthe drive means, another drive means disposed to be operated for tiltingthe furnace, means responsive to the operation of the plunger drivemeans for con trolling the operation of the tilting drive means, thetilting drive means and the plunger drive means cooperating to controlthe level of the molten metal in the tundish, and means responsive tothe level of molten metal in the mold for controlling the operation ofthe dynamo-electric machine.

2. In a system for controlling the flow of metal from a tundish suppliedby a tiltable furnace to a mold disposed to receive the metal, thecombination therewith of, means disposed in operative relation with thetundish for acting directly on the molten metal contained thereinindependently of the operation of the tiltable furnace for changing thelevel of molten metal in the tundish, a dynamo-electric machineconnected to control the operation of the direct acting means, drivemeans disposed to be operated for tilting the furnace, means responsiveto the operation of the direct acting means for controlling theoperation of the tilting drive means, the tilting drive means and thedirect acting means cooperating to control the level of the molten metalin the tundish, and means responsive to the level of molten metal in themold for controlling the operation of the dynamo-electric machine.

3. In a system for controlling the flow of metal from a tundish suppliedby a tiltable furnace to a mold disposed to receive the metal, thecombination therewith of, means disposed in operative relation with thetundish for acting directly on the molten metal contained thereinindependently of the operation of the tiltable furnace for changing thelevel of molten metal in the tundish, a dynamo-electric machineconnected to control the operation of the direct acting means, meansdisposed to be operated for tilting the furnace in a predetermineddirection, means responsive to the operation of the direct acting meansfor controlling the operation of the tilting means in said predetermineddirection, the tilting means and the direct acting means cooperating tocontrol the level of the molten metal in the tundish, means disposed tobe actuated to control the operation of the tilting means in a directionopposite to said predetermined direction irrespective of the operationof the direct acting means, and means responsive to the level of moltenmetal in the mold for controlling the operation of the dynamoelectricmachine.

References Cited in the file of this patent UNITED STATES PATENTS1,139,888 Mellen May 18, 1915 2,246,907 Webster June 24, 1941 2,536,325Tama Jan. 2, 1951 2,683,294 Ennor et al July 13, 1954 2,707,720 Tama May3, 1955

